As discussed in Patent Document 1, a light flux incident on an image sensor from an imaging lens includes a large number of components of light focused in an oblique direction in addition to components vertically incident on an imaging plane of the image sensor. Circles of confusion of light collected by microlenses respectively arranged to correspond to pixels on the imaging plane are not necessarily formed uniformly in a central portion of each of the pixels in the image sensor, and are shifted from the center of each of the pixels depending on a position of the pixel. Even if a plane having a uniform illuminance is photographed in a light receiving unit arranged in a peripheral portion of the imaging plane of the image sensor, therefore, an amount of received light is made smaller than that in a light receiving unit in a central portion of the imaging plane in the vicinity of an optical axis of the imaging lens. As a result, luminance shading, which causes a light-dark strain because brightness is not uniform depending on a position of the imaging plane, occurs in an imaging signal output from the image sensor, resulting in a deteriorated image quality.
In Patent Document 2, an image acquisition device causes gain control means to acquire lens information including at least information relating to a position of an exit pupil while acquiring an image signal to correspond to a position on an imaging plane of an image sensor, to control a gain for each color component of the image signal depending on lens information of various interchangeable lenses and a distance from the center of the imaging plane, and the interchangeable lens causes information supply means to supply lens information including information relating to a position of an exit pupil and a diaphragm value of a photographic lens to the image acquisition device as one of parameters used when the image acquisition device controls the gain for each color component of the image signal.
In Patent Document 3, a lens unit ROM (Read-Only Memory) provided in a lens unit of a digital single-lens reflex camera stores identification data for identifying a photographic lens. A system control circuit on the side of a camera body reads out the identification data. The digital signal processing circuit reads out, out of lens data exhibiting shading properties of a lens, which are previously stored in a camera ROM, the lens data about the photographic lens based on the identification data. Further, a digital signal processing circuit reads out image sensor data exhibiting shading properties of a CCD (Charge Coupled Device) from the camera ROM 56, and corrects shading of an image recorded in an image memory based on the lens data and the image sensor data.
Patent Document 4 includes a lens barrel for focusing a subject image on imaging means, correction value recording means for recording a correction value of a chromatic aberration of magnification, a distortion aberration, or shading, which is caused by the lens barrel, and output means for associating an image of the subject image focused on the imaging means and the correction value caused by the lens barrel, which is recorded on the correction value recording means, and outputting them to another communication equipment or a recording medium so that the image and correction information of the image can be recorded in association with each other, and a preferable image can be acquired by correcting various inconvenient phenomena caused by the lens barrel are corrected in an apparatus that outputs the image.